Interpretive Summary: Two phorid parasitoids of fire ants in Brazil were active at different times of the day. Pseudacteon litoralis was most active in the early morning and evening while P. tricuspis was most active during the afternoon. These observations suggest that more than one species may be needed for introduction in biological control programs.

Technical Abstract:
At least 18 species of Pseudacteon phorid parasitoids attack fire ants (Williams & Banks 1987, Pesquero et al. 1993, Disney 1994, Porter et al. 1995a). The high species richness of these phorid parasitoids and the behaviors exhibited by fire ants in their presence (Porter et al. 1995a) suggest a long evolutionary history. The absence of natural enemies, such as phorids, may explain why exotic North American populations of fire ants (Solenopsis invicta Buren) are much larger than those found in their native Brazil (Porter et al. 1992, 1996).